This invention relates to variable speed clutch drives, and particularly to those including engine torque responsive means. The conventional torque responsive drive incorporates a spring in the driven pulley assembly for urging an angularly and axially movable disc toward a second disc fixed to a driven wheel shaft. Increases in engine torque give rise to increases in belt tension, the latter producing an angular movement of the movable disc on the shaft. Axial movement is thereby induced by two interacting cam surfaces, one of which is fixed to the movable disc, the other to the driven wheel shaft. Thus, an increase in belt tension will rotate the movable disc through a small angle relative to the fixed disc, during which the movable disc will be urged toward the fixed disc by the cam surfaces to provide a low speed ratio when high torque must be delivered to the rear wheel as, for example, during acceleration of the vehicle. Upon reduction of belt tension, the movable disc will be urged away from the fixed disc, resulting in a speed ratio gain under conditions of decreased torque. Manufacture of the prior art cam mechanisms has proved to be fairly expensive, particularly the machining costs resulting from the close tolerances required. Moreover, prior art cam mechanisms have resulted in the addition of considerable weight and bulk to the driven pulley assembly.